The use of Electrospray Ionization combined with mass spectrometry has increased dramatically in recent years. The Electrospray technique has evolved as a powerful tool used for wide range of applications found in the environmental, analytical chemistry and molecular biology fields. The Phase I feasibility study demonstrated that the using mechanical vibration nebulization to assist the Electrospray process greatly expands its optimal range of operation. By assisting the Electrospray process with ultrasonic nebulization, high conductivity solutions, aqueous solutions and liquid flow rates ranging from 0.5 ul/min to well over 400 ul/min can be sprayed. Stable negative ion mode Electrospray operation can be achieved with this technique, eliminating the need for oxygen gas flow at the needle tip. In the proposed Phase II research and development plan the initial work begun during Phase I will continue. During Phase II the ultrasonic nebulizer design will be improved until optimal performance is achieved. The nebulizer driver circuitry will be developed and the Electrospray ion source will be redesigned to maximize performance with this new technique. These development efforts will be combined with an extensive testing program to qualify performance particularly for a wide range of LC/MS operating conditions.